In general, silver (Ag) provides a strong sterilizing effect and deodorizing effect, and is also excellent at preventing electromagnetic waves or geopathic stress. Moreover, it is also well-known that silver (Ag) is excellent at radiating anions and far-infrared rays and provides strong anti-bacterial and antimycotic effects. Furthermore, silver (Ag) is known as one of essential elements to boost immunity in the body. It is also well-known that silver (Ag) ions prevent functions of enzymes during oxygen metabolism of bacterium or germs and kill pathogenic organisms as strong catalysts after being easily absorbed into the human body.
Additionally, silver (Ag) has been widely used as an antidote because having excellent detoxifying properties, and has been used as silver spoons or silverware at Court because being discolored due to neutralization or absorption with heavy metals or various noxious ingredients.
In connection with records on effects of silver, Bencao Gangmu, which is a traditional Chinese medicinal book, tells that silver extends a user's life because it makes the five viscera easy, makes mind and body stable, drives evil strength out, and makes the user feel refreshed. Moreover, Dongeuibogam, which is a traditional Korean medicinal book, tells that silver is effective against mental diseases, such as epileptic fit and convulsion, and female disorders, such as fluor genitalis.
Conventional methods for manufacturing silver wires or conductive fibers are generally divided into: a thread mixing method of putting and mixing powder of fine silver nano-particles into ingredients of thread and spinning the mixture in such a way that silver particles are impregnated into the thread; and a coating method of coating the surface of a woven fabric or thread with silver using a binder.
First, for the thread mixing method, Korean Patent No. 613,189 discloses a method of manufacturing silver nano synthetic fibers. As shown in FIG. 1, the method of manufacturing silver nano synthetic fibers includes the steps of: (S100) stabilizing silver nano-particles through preprocessing and coating the surface of the silver nano-particles with polymer to prevent silver nano-particles from getting together; (S200) drying material polymerization chips and mixing the preprocessed silver nano-particles with the dried chips; and (S300) melting and spinning the material polymerization chips to which the preprocessed silver nano-particles are mixed to thereby obtain silver nano synthetic fiber yarns on which the silver nano-particles are dispersed evenly.
The step (S100) of preprocessing the silver nano-particles includes the steps of: (S110) coating the silver nano-particles with silicon oxide to stabilize the silver nano-particles; and (S120) coating the surfaces of the silver nano-particles, which are coated with silicon oxide, with polymer.
The method of manufacturing silver nano synthetic fibers is one of various kinds of the thread mixing method, and when being applied to thread, especially, in case of synthetic fiber thread, includes the steps of putting and mixing powder of fine silver nano-particles into ingredients of thread and spinning the mixture in such a way that silver particles are impregnated into the thread.
However, the method has a difficulty to evenly disperse silver particles to the thread, and is deteriorated in efficiency compared with an added amount of silver because it cannot show the inherent properties of silver in case of silver particles which do not protrude to the interior surface of the thread even though the silver particles are dispersed evenly. Moreover, when the silver impregnated amount is increased during spinning of the thread, the thread is not spun smoothly, and hence, there may occur defects such as break of the thread. In case of natural materials such as cotton besides the synthetic fiber thread, there is a limitation in use because silver cannot be impregnated into the natural materials.
Furthermore, silver fiber obtained through the thread mixing method is deteriorated in anti-electromagnetic effect and conductivity in an aspect of electrical characteristics, and just synthetic fiber thread including polyester can achieve the anti-electromagnetic effect and conductivity, but in this instance, it is difficult to provide a good silver effect because the silver impregnated amount is very small.
As a prior art according to the thread mixing method, Korean Patent No. 573,029 entitled “silver fiber and method of producing the same” discloses a method of producing thread by mixing polymer and silver particles and spinning the mixture through a nozzle. Silver particles are dispersed evenly inside the thread obtained through the producing method, but the method also has the same problem as mentioned above.
Furthermore, Korean Patent No. 588,763 discloses a method of producing anti-bacterial fiber containing silver nano-particles and anti-bacterial fiber produced through the method. In Korean Patent No. 588,763, the anti-bacterial fiber produced through the method contains silver nano-particles evenly dispersed inside a polymer without cohesion by adding silver nano-particle colloidal solution to the preheated polymer and removing moisture during rotation. However, the method also has the same problems as the above because the silver nano-particles and the polymer are mixed and spun together.
Meanwhile, as a prior art in relation with the coating method, Korean Patent Laid-open No. 2004-78826 discloses a method of producing functional fiber containing nonferrous metals. In Korean Patent Laid-open No. 2004-78826, the method of producing functional fiber includes the steps of: making fiber thread discharged through a nozzle after melting raw materials; putting purified water mounted at a nozzle outlet in water tanks; arranging a number of discharge electrodes on a fiber passing through the nozzle in a diagonal direction; supplying electric power in such a fashion that electric power is supplied alternatingly by the water tanks which are in alternating arrangement so that the discharge electrodes are discharged evenly; passing fiber thread through the water tanks so that the fiber thread is bound to fiber.
However, the method of adding nonferrous metals to fiber by discharging the discharge electrodes is a sort of the silver coating method and has several problems in that the process is complicated and inconvenient and production costs are increased. Moreover, the method also has other problems in that it is not easy to coat nonferrous metals to fiber evenly because the arrangement of the discharge electrodes is not even, and in that it is difficult to keep the initial anti-bacterial function as it is because the coated silver may be easily come off during washing since coated silver cannot keep a firm binding force.
Furthermore, Korean Patent No. 542,007 entitled “electrically conductive fabric” discloses a conductive fabric which can prevent back-leak of resin and unwinding of thread and provide flexibility, conductivity and electromagnetic shielding performance by forming a metal film, such as silver, copper, nickel, tin, or others, on a synthetic fiber filament through the electroless plating method. However, the conductive fabric obtained through the plating method also has a problem in that the coated silver may be easily come off during washing, and hence, it is difficult to keep the initial anti-bacterial function as it is.
Conventional methods of producing conductive yarns are divided into a compound yarn method, a coating method, and a metal yarn method (metal pulling), and the conductive yarns are related with smart clothing.
In case of the compound yarn, a conductive material or a metal layer produced by decomposing conductive carbon black is taken as a core and a nonconductive layer is covered on the core, so that at least two layers are formed. Additionally, in order to enhance conductivity of the compound yarn, if necessary, the core is manufactured not in a circle but in one of other shapes.
Moreover, the produced conductive yarn has a problem in that it is difficult to properly operate a digital device mounted on smart clothing because it has an electrical performance still lower than the metal yarn made by pulling work.
Korean patent Laid-open No. 2006-122543 discloses conductive yarns used for smart clothing with electrical insulating property, which covers copper metal yarn and metal yarn having diameters ranging from 0.03 mm to 0.08 mm.
As shown in FIGS. 2 and 3, the copper conductive yarn 2 is covered by thread as a covering yarn 1. The covering yarn 1 may be made of PET, nylon, wool, and so on. Additionally, the copper metal yarn 3 may be three strands of yarn.
The conductive yarn can show the function of general conductive yarns because using the copper metal yarn as thread, but is lower in conductivity than silver and does not have the same anti-bacterial function as a conductive yarn using a silver wire. In addition, the conductive yarn using the copper metal yarn has another problem in that its color is changed easily due to oxidation of copper.
Korean Patent No. 706,669 discloses a silver wire combined with silver powder and a system for producing the silver wire. In Korean Patent No. 706,669, the silver wire is made by the steps of: coating silver powder on the surface of thread serving as a core yarn while covering or plying one strand or two strands of thread through a covering machine; and covering the thread with another thread. The silver wire is made by coating the surface of thread with silver particles and covering the coated thread with another thread to thereby prevent the silver particles from being come off.
Such a coated yarn is a conductive yarn that a conductive material is coated on the surface of a nonconductive material and has better conductivity than nonconductive materials, but has a problem in that it is lower in conductivity than metal wires and is low in durability and price competitiveness because it is coated with copper.
Korean Patent No. 688,899 discloses a conductive plied metal yarn and a method of producing the same. In Korean Patent No. 688,899, the conductive plied metal yarn is made by covering and twisting a plurality of conductive materials on the surface of a fiber yarn in such a way as to be large in number of twist and plying and twisting the twisted yarns.
Such a compound yarn is high in tensile strength and provides good electromagnetic shielding performance because using a great deal of metal wires per unit length even though the used amount is different according to weaving forms and used metals. However, the required length of the compound yarn per unit length is increased, resistance is increased. Moreover, if resistance is increased, there may occur a signal distortion when the compound yarn is used as a fabric signal line (conductive yarn or digital yarn) for smart clothing.
Because metal wires generally provides good characteristics as resistance is low, metal wires with a large cross-sectional area show good characteristics, but considering a wear sensation and production costs of fabrics obtained using the metal wires, metal wires with a small cross-sectional area are better than those with large cross-sectional area. Accordingly, in order to provide a good wear sensation and enhance conductivity, metals with high conductivity must be made into fine wires.